Implantable medical devices are used to treat many conditions. Implantable devices such as pacemakers and defibrillators include electronics mounted within a housing. The electronics are typically operatively connected to a lead which is implanted on or in the heart. The leads implanted in or about the heart can be used to reverse certain life threatening arrhythmia, or to stimulate contraction of the heart. Electrical energy is applied to the heart via electrodes on the leads to return the heart to normal rhythm.
An implantable device can include a hermetically sealed device housing electrically and mechanically connected to a header. The header is used to couple a conductor of the lead with the electronics of the implantable device. The header is electrically connected to the device housing by an electrical feedthrough assembly including feedthrough wires that extend from outside to inside the housing to connect to the electronic components within the housing.
The feedthrough assembly provides a mechanism for electrical signal transfer through the hermetically sealed housing. In some cases, a ferrule of the feedthrough assembly needs to be at electrical ground potential. In some feedthrough assemblies, such as discussed in U.S. Pat. No. 6,586,675, the ground lead connection extends through an insulator of a feedthrough assembly and is then connected to the ferrule on the exterior of the housing.